There's a poll on MetsBlog asking whether the Mets should sign Barry Bonds. People are against it, about 2-1. Without rehashing the entire argument, I'll just post the following statistics:

Barry Bonds OPS in 2007: 1.045
Combined Mets LF OPS in 2008: .625

Just to put it into perspective, if Bonds played 2/3 of the time (which is what he did in 2007), the above difference would be worth about 6 wins over the course of a season (Bonds's defense might knock it down to 5 wins).